Plant hormones have been intensively studied for decades for their diverse and complex effects on the plant life. Of the five main hormones-auxins, ethylene, abscisic acid, cytokinins and gibberellins-the molecular signaling and mode of action of ethylene has been the most fully resolved. This progress was made chiefly in the 1990s by the cloning of genes corresponding to mutations in ethylene production and signaling.
Ethylene (C2H4) is a gaseous plant hormone that affects myriad developmental processes and fitness responses in plants, such as germination, flower and leaf senescence, fruit ripening, leaf abscission, root nodulation, programmed cell death and responsiveness to stress and pathogen attack. Over the past decade, genetic screens have identified more than a dozen genes involved in the ethylene response in plants. Ethylene governs diverse processes in plants, and these effects are sometimes affected by the action of other plant hormones, other physiological signals, and the environment, both biotic and abiotic. For example, it is known that cytokinin can cause ethylene like effects through the action of ethylene. In addition, abscisic acid can inhibit ethylene production and signaling. Auxin and ethylene are also known to cooperate in various physiological phenomena. From what is currently known, in general ethylene does not appear to be strictly required for the plant's life cycle, but it does significantly modify development and condition response to stresses.
What is needed in the art is a means to improve agronomic performance in plants, particularly cereal crops such as maize, by modulating ethylene mediated responses in plants.